Interpretive Summary:
Scientific names provide the best means for scientists to share information gathered from plant studies. A published set of globally accepted rules, the International Code of Botanical Nomenclature, determines the correct name to be used for a given plant. One such rule dictates that the first name published from 1753 on, when Linnaeus first established binomial species names, is the one that must be used, so species names from the oldest references have greater importance and must be accounted for. One of the earliest sources of American plant names is Pehr Loefling’s Iter Hispanicum of 1758. Identification of the plants he named has always been difficult, however, because there are no illustrations or specimens to help with this, thus many of his names have been wrongly ignored by later botanists. Our analysis of Loefling’s publication reveals that 31 new genera and 15 new species were created therein for Venezuelan plants. The identity of each of these names is evaluated, and currently 9 of the genera and 2 of the species are still being used. The remaining names are not in current use, although under the rules some of these should be because of their early age, but that would upset scientific communication, which has long used other later names for the plants involved. The implications of this dilemma are discussed for each name and possible solutions for dealing with the troublesome cases under the International Code are evaluated.

Technical Abstract:
Loefling’s Iter Hispanicum (1758) and its subsequent translations, editions, issues, and facsimiles are analyzed for their impact on the nomenclature of American vascular plants. The book, edited by Linnaeus and posthumously published, contains descriptions of plants found in Venezuela (as well as in the Iberian Peninsula). For American plants the original volume (1758) is the source of 31 new genera, 15 new species, and one replaced name, and a German translation (1766) is the source of an additional two new species. Many of these nomenclatural innovations have been ignored, overlooked, or intentionally suppressed, some for centuries. Other names in the Iter Hispanicum have been misinterpreted. We examine the reasons for considering these 48 names to be validly published and the nomenclatural ramifications. In the interests of nomenclatural stability we are forced to conclude that the names of at least ten taxa described by Loefling should be rejected: Ayenia sidiformis Loefl., Cofer Loefl., Cruzeta Loefl., Cruzeta hispanica Loefl., Edechia inermis Loefl., E. spinosa L., Justicia putata Loefl., Menais Loefl., Muco Loefl., and Samyda parviflora Loefl. Likewise the names of at two species described by Linnaeus that are tied to the Iter Hispanicum should be rejected: Menais topiaria L. and Spermacoce suffruticosa L. Finally, we select neotypes for Gaura fruticosa Loefl. and Waltheria melochioides Loefl.